Chair

ABSTRACT

Although conventional chairs with armrests have arm mounts which are rotatably movable from their original position to in front of the person in the chair, they tend to make unnecessary motions such that part of the arm mount protrudes so far outward during its rotation so that the person must move the chair back or assume an uncomfortable position to prevent the arm mount from interfering with the desktop, him or herself. In addition, a supporting structure of the arm mounts is weak and unstable. The present invention provides a chair with armrests which includes arm supports being attached to the sides of a chair body, arm mounts supported by the arm supports and a controlling means which controls at least the arm mounts so that they can move around the person in the chair in a substantially regular path between a first use position on a side of the person and a second use position in front of the person.

FIELD OF THE ART

[0001] The present invention relates to a chair with movable armreststhat are comfortable and easy to use.

BACKGROUND ART

[0002] In recent years, desktop OA (office automation) equipment, suchas personal computers, has come to be used more frequently in officesand the like. As chairs become more functional, reclining against theback of a chair has been found to be the most comfortable position foroperating a personal-computer keyboard or the like. Because a person ina chair tends to work at a desk with his or her arms stretched forward,it is preferable that the person use part of the desktop as an armrestto reduce the load on the arms. However, if the person cannot place thearms on the desktop because he or she is in a reclined position, thedesktop is not sufficiently wide, or the person cannot get close enoughto the desktop due to occupied space under the desk, the person cannotuse the desktop as an armrest. Particularly when operating a keyboard, aperson in a chair tends to hold his or her arms closer together than thedistance between his or her shoulders. Thus, armrests that can be placedin front of the person are needed.

[0003] Chairs are proposed with armrests that can be moved from theiroriginal position to in front of a person in the chairs when he or sheoperates a personal computer. Such chairs include those with armrestsconsisting of arm supports attached to the sides of the chair body, andarm mounts, each of which are rotatably attached to an arm support usingone shaft, and those that are designed to rotatably connect an armsupport to a connecting member using one shaft, and an arm mount to theconnecting member also using one shaft, with the connecting memberinterposed between the arm support and arm mount.

[0004] However, because a chair that is adapted to turn an arm mountusing one shaft is unstable and weak, the shaft is likely to be damagedif a load is exerted at a point too far from the shaft. In addition, therange of rotation of the arm mount around the shaft is limited, so thatthe arm mount cannot be moved far in front of a person in the chair.

[0005] A chair is available that is adapted so that an arm mount turnsaround two shafts at both ends of one free-end link connecting an armsupport and the arm mount together. Although such an arrangement allowsthe arm mount to move more widely, it poses the following problem: partof the arm mount protrudes so far outward during its rotation from theside of a person in the chair to his or her front, that he or she mustmove the chair back or assume an uncomfortable position to prevent themount from interfering with the desktop and him or herself. In addition,the arm mount may be damaged if a load is applied to the mount when itis protruding far outward. If the distance between the two shafts isdecreased to solve these problems, the movement of the arm mount islimited to a narrow range, thus preventing the arm mount from beingfully moved from its regular position to in front of the person in thechair. As is obvious from the above, conventional armrests areuncomfortable and difficult to use.

DISCLOSURE OF THE INVENTION

[0006] In view of the foregoing, the present invention was designed as achair with armrests that can be used as necessary by controlling the armmounts so that they follow the figure of the person in the chair.

[0007] A chair according to the present invention that includes a chairbody with armrests attached to its sides, wherein the armrests includearm supports and arm mounts, with the arm supports being attached to thesides of the chair body and the arm mounts being supported by the armsupports, and a controlling means for controlling at least the armmounts so that they can move around a person in the chair in a regularpath between a first use position on the sides of the person sitting onthe chair body and a second use position in front of the person, isprovided between the chair body and the arm supports or in part of thearmrests.

[0008] Such an arrangement allows at least the arm mounts to move aroundthe figure of a person in a chair between the first use position on thesides of the person and the second position in front of the person.Thus, the person in the chair places his or her arms on the arm mountsin the first use position when he or she is performing no operation athis or her desk, and the person can move the arm mounts to the seconduse position and effectively use them as armrests when he or sheperforms an operation at his or her desk, such as using a personalcomputer. Because the arm mounts follow a substantially regular pathunder the control of the controlling means when moving to the second useposition, it is not necessary for the person in the chair to avoid thearm mounts. Moreover, the arm mounts make only necessary motions,without protruding too far forward or to the side, thus increasingarmrest stability.

[0009] In particular, to appropriately move only the arm mounts with themounts stably supported by the arm supports, it is desirable that, usingan arm supporting means, the arm supports support the arm mounts so thatthe arm mounts can move between the first and second use positions andthe controlling means can control the movement of the arm mounts throughthe use of the supporting means.

[0010] A preferable method of properly moving an arm mount is to use alink mechanism as a supporting means and controlling means by connectingthe arm mount through the link mechanism to an arm support. To make thelink mechanism extremely simple, it is desirable that it constitutefirst and second link elements that are rotatably attached to theconnections between the arm support and the arm mount, that at least thefirst link element be used as the supporting means, and that the firstand second link elements constitute the controlling means.

[0011] To appropriately rotate an arm mount using such a link mechanism,it is preferable that the tetragon formed by the straight linesconnecting attachment holes in the first and second link elements not bea parallelogram. To allow the arm mount to follow an appropriate path, apreferable link mechanism is intended to meet the followingrequirements: the first link element rotates a hole for attachment tothe arm mount from an obliquely rear outside position to an insideposition, with a hole for attachment to the arm support at the center ofrotation; the second link element rotates the hole for attachment to thearm mount from an obliquely rear outside position to an obliquely frontoutside position, with the hole for attachment to the arm support at thecenter of rotation; and the straight line connecting the hole forattaching the first link element to the arm mount and the hole forattaching the second link element to the arm mount rotates between thefirst and second use positions, from the position at which the line isnearly in the longitudinal direction of the arm mount to the position atwhich the line is nearly in the lateral direction of the arm mount.

[0012] To effectively limit the range of rotation of the first andsecond link elements through the use of the link mechanism, the firstand second link elements are adapted so as to interfere with each otherat or near the first and second use positions.

[0013] To improve arm-mount support strength and maintain a regulararm-mount path, it is preferable that the second link element, togetherwith the first link element, supports the arm mounts, and that the linkmechanism uniquely determines the arm-mount path.

[0014] Another link mechanism that allows the arm mounts to move in asubstantially regular path, while allowing slight deviation from thepath is adapted so that the distance between the attachment holes in thesecond link element changes due to deformation of an elastic bodyforming the second link element, such as a spring, when the arm mountsmove from the first use position to the second use position.

[0015] Still another link mechanism that allows the entire armrests,that is, the arm mounts and arm supports, to move in a substantiallyregular path around a person in a chair between the first and second usepositions is provided with a controlling means that rotates the armsupports, together with the arm mounts, between the chair body and armsupports around the person. To allow the armrests to move smoothlywithout interfering with the person, the arm supports are preferablycurved or bent to prevent them from interfering with the person when heor she moves between the first and second use positions.

[0016] To ensure that the arm mounts serve as armrests when a person ina chair such as that described above operates a personal computer, it ispreferable that a pair of armrests be disposed on both sides of thechair body, and that the ends of the arm mounts butt against each otherwhen the pair of arm mounts is placed in the second use position.

[0017] As described above, a chair according to the present inventionhas armrests on the sides of the chair body. Using controlling meansprovided in the armrests or between the chair body and arm supports, thearmrests, that is, the arm mounts supported by the arm supports attachedto the sides of the chair body, are controlled so that at least the armmounts move around the person in the chair in a substantially regularpath between the first use position on the sides of the person and thesecond use position in front of the person. Thus, when he or she is notat his or her desk, the person in the chair can place his or her arms onthe arm mounts in the first use position to assume a comfortableposition. In addition, when he or she performs an operation, such asusing a personal computer, at his or her desk, the person in the chaircan stretch his or her arms forward on the arm mounts in the second useposition nearly in front of him or her, to effectively use the armmounts as armrests. The person in the chair can make the space betweenthe arms wider or narrower than the width of his or her shoulders toplace his or her arms on the arm mounts in the second use position, sothat he or she can work more freely. Under the control of thecontrolling means, at least the arm mounts move in a substantiallyregular path through an angle of approximately 90° or slightly greaterfrom the first use position to the second use position. Thus, the armmounts make only necessary movements, without protruding significantlyoutward or inward, enabling the person in the chair to move the armrestssmoothly and stably without moving the chair back or avoiding the armmounts, even if there is little space between the chair or person andthe desk or the like.

[0018] Such a chair arrangement makes the arm mounts more stable withrespect to the arm supports and allows only the arm mounts to be movedappropriately if the arm supports are used to support the arm mountsbetween the first and second use position, so that the mounts can movewith respect to the arm supports and movement of the arm mounts can becontrolled using the controlling means.

[0019] If the arm mounts are connected through the link mechanism, whichserves as a supporting and controlling means, to the arm supports, thearm mounts can be effectively supported and moved in an appropriatepath. Particularly if the link mechanism consists of the first andsecond link elements, which are rotatably attached to the connections ofthe arm supports and arm mounts, and the controlling means consists ofthe first and second link elements, with at least the first link elementbeing used as the supporting means, the link mechanism can be providedwith a simple structure. Moreover, if the tetragon formed by thestraight lines connecting the four attachment holes in the first andsecond link elements is not a parallelogram, a link mechanism consistingof the two link elements can be used to smoothly move the arm mountsaround the person in the chair when two of the four sides of thetetragon are secured.

[0020] Specifically, a simple link mechanism that moves the arm mountsin a substantially regular path around the person in the chair can beprovided if arrangements are made to meet the following requirements:the first link element is adapted to rotate its holes for attachment tothe arm mounts from an obliquely rear outside position to an insideposition, with its holes for attachment to the arm supports at thecenter of rotation; the second link element is adapted to rotate itsholes for attachment to the arm mounts from an obliquely rear outsideposition to an obliquely front outside position, with its holes forattachment to the arm supports at the center of rotation; and a straightline connecting the hole for attaching the first link element to the armmount with the hole for attaching the second link element to the armmount rotates between the first and second use positions, from theposition at which the line is nearly in the longitudinal direction ofthe arm mount and to the position at which the line is nearly in thelateral direction of the arm mount.

[0021] If the first and second link elements are adapted so as tointerfere with each other at or near the first and second use positions,the link mechanism can effectively be used to limit the range ofrotation of the link elements.

[0022] If the second link element is adapted so as to support the armmounts like the first link element, and these two link elements are usedto uniquely determine the arm-mount path, the arm-mount support strengthcan effectively be increased, and the arm mounts can be moved in aregular path.

[0023] If the second link element is formed using an elastic body suchas a spring and the distance between the attachment holes in the secondlink element is changed by deforming the elastic body when the armmounts move from the first use position to the second use position, themovement path of the arm mount can be varied slightly with the path keptsubstantially regular, and the arm mounts can be adapted so as to be atthe first and second use positions. Thus, the arm mounts can easily bemoved regardless of the physical build and position of the person in thechair.

[0024] In addition, if a controlling means is provided between the chairbody and arm supports to turn the arm supports together with the armmounts, the armrests can be moved in a substantially regular pathbetween the first and second use positions, thus allowing the arm mountsto be used effectively as armrests. Particularly in such a case, curvingor bending the arm supports so that they do not interfere with theperson in the chair during arm mount movement allows the arm mounts tomove smoothly.

[0025] In the above-described arrangements, if a pair of armrests isdisposed on the sides of the chair so that the ends of the arm mountsbutt against each other when both arm mounts are at the second useposition, no gap forms between the arm mounts at the second useposition, thus allowing the arm mounts to be used as reliable armrestswhen the person in the chair works on a personal computer with his orher arms stretched forward.

BRIEF DESCRIPTION OF THE DRAWINGS

[0026]FIG. 1 is a general perspective view of an embodiment of thepresent invention.

[0027]FIG. 2 is an enlarged exploded perspective view of the rightarmrest in the embodiment.

[0028]FIG. 3 illustrates the motions of the right armrest.

BEST MODES OF EMBODYING THE INVENTION

[0029] Referring to the drawings, an embodiment of the present inventionis described below.

[0030] As shown in FIG. 1, a chair according to the embodiment is achair body 1 with a pair of armrests 2 attached to each of its sides.The chair body 1 is structured by positioning a seat 13 on top of asupport 11 at the center of a leg assembly 12, and installing a back 14at the back of the seat 13. The chair body is adapted so that the back14 can rock through the use of an appropriate mechanism. The armrests 2are attached so as to protrude downward from the bottom of the seat 13.

[0031] As shown in FIGS. 1 through 3, the armrests 2 are arm mounts 4that are movably attached through link mechanisms 5 to the upper end ofarm supports 3 attached to the bottom of the seat 13. The arm supports 3have, on their upper ends, a pedestal 31 that is substantiallytrapezoidal as viewed from above.

[0032] The arm mounts 4 completely cover the top of the pedestal 31 whenthey are placed in such a first use position X that their lengthdirection is nearly in the lateral direction of the seat. The armmounts, which are board-shaped, are supported by the pedestal 31 whenthey overhang forward, backward, and sideward. Pads made of a cushionedmaterial are attached to the arm mounts 4 so that the pads cover the topof the mounts. Here, the pads are not shown or described.

[0033] As shown in FIGS. 2 and 3, a link mechanism 5 includes a firstlink element 51 and a second link element 52. The first link element 51,which has a predetermined thickness and is substantially rhombic asviewed from above, is disposed between the pedestal 31 and the bottom 41of the arm mount 4. The first link element has a first attachment hole51 a that is located in a corner 51 x on the longer diagonal, is a bosshole, and opens upward, and a second attachment hole 51 b in thediagonally opposite corner 51 y that is also a boss hole and opensdownward. If a bolt 53 is inserted, the first attachment hole 51 a canbe rotatably combined with a threaded hole 32 at the front inside corneron top 31 a of the pedestal 31. If another bolt 53 is inserted, thesecond attachment hole 51 b can be rotatably combined with a threadedhole 42 provided near the center, but slightly in the longitudinaldirection of the arm mount 4 on its bottom 41.

[0034] The second link element 52, which is almost as thick as the firstlink element, 51 and is rod-shaped, has a attachment hole 52 a that is aboss hole and opens upward at one end 52 x, and a second attachment hole52 b that is also a boss hole and opens downward at the other end 52 y.If a bolt 53 is inserted, the first attachment hole 52 a can berotatably combined with a threaded hole 33 in a rear inside corner ontop 31 a of the pedestal 31. If another bolt 53 is inserted, the secondattachment hole 52 b can be rotatably combined with a threaded hole 43provided at the rear edge facing away from the arm mount 4. The firstand second link elements 51 and 52 together constitute supporting meansA for supporting the arm mount 4 and controlling means B for controllingthe arm mount, so that it moves in a regular path around a person in thechair. The attachment holes 51 a, 52 b, 52 a, and 52 b are disposed sothat the tetragon formed by the straight lines connecting theseattachment holes is not a parallelogram.

[0035] The link mechanism 5 causes the arm mount 4 to move in a regularpath around a person in the chair between the first use position X on aside of the seat 13 and the second use position Y at the upper front ofthe seat 13. For the right arm mount, operation of the link mechanism 5is specifically described below. As shown in FIG. 3, when the right armmount 4 is moved forward from the first use position X by hand, thefirst link element 51 rotates the second attachment hole 51 bcounterclockwise as viewed from above, with the first attachment hole 51a at the center of rotation so as to move the second attachment hole 51b in an arc from an obliquely rear outside position to an insideposition above the seat 13. The second link element 52 rotates thesecond attachment hole 52 b counterclockwise as viewed from above, withthe first attachment hole 52 a at the center of rotation so as to movethe second attachment hole 52 b, in an arc, along a side 13 a of theseat 13 from an obliquely rear outside position to an obliquely frontoutside position. Here, a straight line connecting the second attachmenthole 51 b in the first link element 51 to the second attachment hole 52b in the second link element 52 (the straight line is represented by achain line in the figure) rotates from the position at which thestraight line is nearly in the longitudinal direction of the arm mount,which corresponds to the first use position X, to the position at whichthe straight line is nearly in the lateral direction of the arm mount,which corresponds to the second use position Y. As a result, themovement path of the right arm mount 4 is determined uniquely so that itmoves from the first use position X to the second use position Y in aregular path around the person in the chair. As with the right armmount, the left arm mount 4 also moves in a regular path around theperson in the chair.

[0036] When the right and left arm mounts 4 move to the second useposition Y, their ends 4 a, facing inward, butt against each other, thusstopping the arm mounts 4. When one of the right and left arm mounts 4moves to the second use position Y, that arm mount 4 stops in a positionnearer to the person in the chair than the second use position Y. Thatis, in the position nearer to the person in the chair than the seconduse position Y, the first and second link elements 51 and 52 are made tointerfere with each other so as to limit the range of rotation of bothlink elements 51 and 52. The first and second link elements 51 and 52are also made to interfere with each other near the first use position Xso as to limit the range of rotation of both link elements.

[0037] A chair according to this embodiment, arranged as describedabove, has a pair of armrests 2 attached to the sides of the chair body1, with each armrest consisting of the arm support 3 and the arm mount 4supported by the arm support. Using the controlling means B provided inthe armrests 2, the arm mounts 4 are controlled so as to move in aregular path around the person in the chair between the first useposition X on each side of the person and the second use position Ysubstantially in front of the person. Thus, the person in the chairplaces his or her arms on the arm mounts 4 in the first use position Xto assume a comfortable position. Alternatively, when performing anoperation at his or her desk, such as using a personal computer, theperson stretches his or her arms forward on the arm mounts 4 in thesecond use position Y to use the mounts as armrests. As described above,the person in the chair can use the arm mounts 4 conveniently. Whenusing the arm mounts 4 in the second use position Y, the person in thechair can make the space between the arms wider or narrower than thewidth of his or her shoulders to enable an operation, such as using apersonal computer, to be performed more freely. Moreover, the person inthe chair can place his or her arms on the arm mounts 4 to allow them torelax. Under the control of the controlling means B, the arm mounts 4move in a substantially regular path through an angle of approximately90° or slightly greater between the first and second use positions.Thus, the arm mounts 4 make necessary movements only, withoutsignificantly protruding outward or inward, enabling the person in thechair to easily and stably move the arm mounts 4 without moving thechair back or avoiding the arm mounts.

[0038] Particularly in this embodiment, the link mechanisms 5constituting the supporting means A support the arm mounts 4 so thatthey can move with respect to the arm support 3 between the first andsecond use positions. In addition, the link mechanisms 5 constitute thecontrolling means B for controlling the movement of the arm mounts 4.These arrangements increase the stability of the arm mounts 4 relativeto the arm support 3, and allow only the arm mounts 4 to be movedappropriately. That is, because the arm mounts 4 are connected to thearm supports 3 through the link mechanisms 5, which serve as both thesupporting means A and controlling means B, the arm mounts 4 can besecurely supported using a reduced number of parts, and can easily bemoved in an appropriate path.

[0039] The link mechanisms 5 consist of the first and second linkelements 51 and 52 rotatably attached to the connections between the armsupports 3 and the arm mounts 4. The link elements 51 and 52 are used asthe supporting means A and controlling means B, thus allowing the linkmechanisms 5 to be simplified and the arm mounts 4 to be made morestable. In addition, because the tetragon formed by the straight linesconnecting the attachment holes 51 a, 51 b, 52 a, and 52 b in the firstand second link elements is not a parallelogram, a so-callednon-parallel link mechanism with two sides secured allows the arm mounts4 to be smoothly around the person in the chair.

[0040] Specifically, the link mechanisms 5 cause the first link element51 to rotate the second attachment hole 51 b for attaching the armsupport 31 to the arm mount 4 from an obliquely rear outside position toan inside position, with the first attachment hole 51 a for attachingthe arm support 3 to the pedestal 31 at the center of rotation. The linkmechanisms also cause the second link element 52 to rotate the secondattachment hole 52 b for attaching the arm support 3 in the arm mount 4from an obliquely rear outside position to an obliquely front outsideposition, with the first attachment hole 52 a for attaching the armsupport 3 to the pedestal 31 at the center of rotation. Thus, a straightline connecting the second attachment hole 51 b in the first linkelement 51 to the second attachment hole 52 b in the second link element52 rotates between the first use position X and the second use positionY from the position at which the straight line is nearly in thelongitudinal direction of the arm mount to the position at which thestraight line is nearly in the lateral direction of the arm mount. Thesearrangements allow the arm mounts 4 to move around the person in thechair.

[0041] Because the first and second link elements 51 and 52 are adaptedso as to interfere with each other near the first and second usepositions X and Y, the link mechanisms 5 can easily and effectivelylimit the range of rotation of the link elements 51 and 52 withoutproviding additional means for limiting the range of rotation of thelink elements 51 and 52.

[0042] In addition, as described above, the first link element 51 andthe second link element 52, which is adapted so as to support the armmounts 4 together with the first link element 51, are used to uniquelydetermine the path of the arm mounts 4. Thus, not only can the supportstrength of the arm mounts 4 be effectively increased, but the armmounts 4 can be prevented from deviating from a regular path when theymove.

[0043] When the pair of arm mounts 4 is placed at the second useposition Y, the ends 4 a of the arm mounts 4 butt against each other,with the length direction of the arm mounts 4 nearly in the lateraldirection of the seat. Thus, there is no gap between the arm mounts 4 atthe second use position Y, enabling the arm mounts 4 to be used asstable, reliable armrests.

[0044] The present invention is not limited to this embodiment. Forexample, a spring or an elastic body may be used as the second linkelement in place of the rod of a predetermined length that is used inthis embodiment. In such a case, the second link element does notfunction as a supporting means, but the first link element does.However, the arm mounts can be moved in almost the same path as in thisembodiment between the first and second use positions. When the armmounts are moved, the path may change slightly. That is, the second linkelement has a predetermined length at the first and second usepositions, while the distance between the ends of the second linkelement, at which the first and second attachment holes are provided,may vary slightly due to elastic deformation of a spring when the armmounts move between the first and second use positions. Thus, even if itis slightly difficult to move the arm mounts to the second use positiondue to the physical build or position of the person in the chair, he orshe can move the arm mounts slightly away from him or herself duringmovement from the first to the second use position, and can return thearm mounts to their original positions at the first and second usepositions. Thus, the arm mounts can be used more conveniently. Ofcourse, an elastic body made of rubber or the like may be substitutedfor the spring.

[0045] In addition to designing the arm mounts so that they can movewith respect to the arm support, providing a controlling means betweenthe arm support and chair body that is used to rotate the arm support ina substantially regular path together with the arm mounts allows the armmounts to be appropriately used as armrests. In such a case, it ispreferable that the arm mounts be curved or bent to prevent the armsupport from interfering with the person in the chair during movement.

[0046] The present invention is not limited to the above embodiment, butvarious modifications can be made without departing from the scope andspirit of the present invention. For example, rail, gear, and beltmechanisms designed to move the arm mounts in a regular path can beapplied to the present invention.

POSSIBLE APPLICATIONS IN INDUSTRY

[0047] As mentioned above, the chair in accordance with the presentinvention is ideally used in offices or the like as a chair witharmrests which can move according to a position of a person in a chair,such as a working position when operating a keyboard on the desk and acomfortable position when reclining against the back of the chair.

1. A chair that includes a chair body and armrests installed on the sides of the chair body, wherein the armrests include arm supports and arm mounts, with the arm supports being attached to the sides of the chair body and the arm mounts being supported by the arm supports, and a controlling means for controlling at least the arm mounts so that they can move in a substantially regular path around a person in the chair, between a first use position on the sides of the person and a second use position in front of the person, is provided between the chair body and the arm supports or in part of the armrest.
 2. A chair according to claim 1, wherein the arm mounts are supported by the arm supports so that the arm mounts can be moved between the first and second use positions by the supporting means, and the controlling means is used to control movement of the arm mounts by the supporting means.
 3. A chair according to claim 2, wherein the arm mounts are connected through a link mechanism to the arm supports, and the link mechanism serves as the supporting means and controlling means.
 4. A chair according to claim 3, wherein the link mechanism consists of first and second link elements that are rotatably attached to the connections of the arm supports and the arm mounts, at least the first link element is used as the supporting means, and the first and second link elements constitute the controlling means.
 5. A chair according to claim 4, wherein the tetragon formed by the straight lines connecting the attachment holes in the first and second link elements is not a parallelogram.
 6. A chair according to claim 5, wherein the first link element rotates a hole for attachment to the arm mount from an obliquely rear outside position to an inside position, with a hole for attachment to the arm support at the center of rotation, the second link element rotates the hole for attachment to the arm mount from an obliquely rear outside position to an obliquely front outside position, with the hole for attachment to the arm support at the center of rotation, and a straight line connecting the hole for attaching the first link element to the arm mount and the hole for attaching the second link element to the arm mount rotates between the first and second use positions, from the position at which the line is nearly in the longitudinal direction of the arm mount to the position at which the line is nearly in the lateral direction of the arm mount.
 7. A chair according to claim 4, 5, or 6, wherein the first and second link elements are made to interfere with each other at or near the first and second use positions, to limit the range of movement of the first and second link elements.
 8. A chair according to claim 4, 5, 6, or 7, wherein the second link element supports the arm mounts together with the first link element, and the link mechanism is used to uniquely determine the path of the arm mounts.
 9. A chair according to claim 4, 5, 6, or 7, wherein the second link element consists of an elastic body, and the distance between the two attachment holes in the second link element is changed by deforming the elastic body when the arm mounts move from the first use position to the second use position.
 10. A chair according to claim 1, wherein the controlling means is provided between the chair body and arm supports so as to rotate the arm supports together with the arm mounts around a person in the chair.
 11. A chair according to claim 10, wherein the arm supports are curved or bent to prevent them from interfering with a person in the chair when he or she moves between the first and second use positions.
 12. A chair according to any of claims 1 through 11, wherein a pair of armrests is disposed on both sides of the chair body, and the ends of the arm mounts butt against each other when the pair of armrests is placed in the second use position. 